CBNNews.com - JERUSALEM, Israel - The U.S. State Department called predictions by an unnamed senior U.S. defense official of an imminent Israeli attack on Iran's nuclear facilities "foolish."

"I have no information that would substantiate that, and I think it's rather foolish of people who often have no clue what they're talking about to assert things and not even have the courtesy to do so on the basis of their name," said State Department spokesman Tom Casey.

The anonymous official told ABC news Tuesday that Washington was concerned about a retaliatory attack against the United States should Israel strike Iran.

According to the official, Israel cannot wait until Iran's Natanz nuclear plant has produced enough enriched uranium to build a bomb, which could be by the end of 2008 or early 2009.

A second scenario that would prompt Israel to attack sooner than later is Iran's attempt to acquire the SA-20 air defense system from Russia.

The report also said Israel may be planning an attack before the next president is sworn in, a point made by former US United Nations Ambassador John Bolton recently.

Meanwhile, a former Israel Defense Forces (IDF) intelligence officer told YNet news Tuesday that the US expects Israel to do "the dirty work" by attacking Iran.

"That way, in case of a global flare-up, Israel could be blamed," said Yossi Kuperwasser, former head of the IDF's Research and Assessment Division.

"Within a year to a year and a half, the Iranians will have enough uranium for a nuclear bomb," he said. "This is also the American intelligence estimate, which at the time was harshly criticized, and rightfully so. As far as we know, they continue their research uninterrupted," he said.

Kupperwasser said the SA-20 air defense system would definitely increase the difficulty of an aerial strike.

"This is a missile system that can protect against missiles and airplanes," he said. "The Iranians have another aerial system today, but they view it as inadequate. Clearly, every addition to the aerial defense system may minimize the effectiveness of an aerial strike," he said.

"The West realizes that this is an Iranian challenge to the existing world order, aiming for Islam to enjoy a different status. Finally people have woken up, but the question is whether officials in the US and Europe realize the gravity at this time. It looks as though everyone is trying to shift the responsibility to someone else, and they believe that ultimately, if nothing changes, Israel will do the job for the West," he said.

"Iran realizes that the West is sensitive to pain and money and won't embark on an operation that would significantly boost oil prices," he said.

"Every time the possibility of a military strike is raised, the [Iranian] Revolutionary Guard's commander speaks out and warns against the chaos. They believe that the likelihood of a strike is low," he said.

"In this poker game, the Iranians are leading at this time. The pressure should be boosted considerably, and it should be made clear that a military move will be carried out if needed," Kuperwasser said.

"If the Iranians believe that the West is serious, they will think twice about whether it is worthwhile for them to continue," he said.